[EM] Approval Strategy A- Question for Rob LeGrand

Kevin Venzke stepjak at yahoo.fr
Thu Nov 20 16:23:08 PST 2003


 --- Dgamble997 at aol.com a écrit : > Hello Rob and List
> Recently I've been trying to develop a spreadsheet model to investigate the 
> effect of the use of different voting systems ( Plurality, IRV, Borda, 
> Condorcet and Approval) on the results of  elections to a multi-member assembly 
> elected in single districts.

Are you looking to show that Plurality, for example, is more likely to be proportional 
than Condorcet?  Random Ballot is easily more proportional than that.  Better yet, 
put a PR method in your model.

My thoughts:
Plurality will be the most proportional because it can occasionally elect a
fluke candidate to represent weird voters.
IRV will be next, electing only mainstream flukes (no other flukes).
Borda will be somewhere around here, although I don't think you'll be able to
model it accurately.  Specifically, how can you account for the incentive for a
party to run multiple candidates?
Approval will be among the least proportional.
Condorcet methods will be last, picking the centrist whenever the voters decide
not to truncate him.

My thought, you see, is that methods which avoid electing centrists are more
likely to represent some other area of the spectrum (perhaps even at random).
Even if such methods can't pick the "group choice" very well, across all districts
the results should be fairly proportional.

> I wanted to use in my model an Approval strategy which Approval supporters ( 
> of which I am not one) say will give a result that is satisfactory to the 
> voters. I decided to use Rob LeGrand's strategy A. Rob said the following about 
> strategy A:
> > Strategy A: Approve all candidates I prefer to the current CRAB
> > first-placer; also approve the first-placer if I prefer him to the
> > second-placer.
> >
> > [S]trategy A always homes in on the Condorcet winner when one exists
> > and all voters use the same strategy.

I have a hard time calling this an Approval strategy, since it seems to require
that CRAB be implemented...

Based on what you posted it looks like you're just doing a single round.  I'm
not sure that's right.  (But I'm also not sure what the precise definition of
CRAB is.)

I suspect you won't be able to model Approval convincingly, if the only
information to begin with is rankings.

If the voters have perfect information, Approval should be Condorcet-like.
Otherwise, I suspect Approval will more often elect off-center.

Kevin Venzke
stepjak at yahoo.fr

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